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Germany warns against "cherry-picking" saying Europeans are in the same boat

U.S. President Barack Obama had told Cameron the U.S. valued the UK's place in the EU

European leaders have warned Britain against the dangers of cherry-picking European Union policy after David Cameron announced Britain would hold a referendum on its European Union membership if his Conservative Party is re-elected in 2015.

Ahead of the British prime minister's speech, U.S. President Barack Obama had also advised Cameron that the United States valued Britain's membership of the European bloc.

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French Foreign Minister Laurent Fabius used similar language in an interview on France Info radio saying Europe could not be "a la carte," Agence France-Presse (AFP) reported.

"Imagine the EU was a football club: once you've joined up and you're in this club, you can't then say you want to play rugby," it quoted him as saying.

"It risks being dangerous for Britain itself because Britain outside of Europe, that will be difficult," Fabius said.

German Chancellor Angela Merkel told reporters that being part of Europe involved compromise.

"Europe also always means that you have to find fair compromises. In this context, we are of course ready also to talk about British wishes but one must keep in mind that other countries also have other wishes," Merkel said.

German Foreign Minister Guido Westerwelle told reporters his country wanted Britain "to remain an active and constructive part of the European Union" and warned against "cherry-picking."

"We strive to create a better Europe, the European Union becoming even stronger with overcoming the debt crisis and regaining global competitiveness," AFP quoted him as saying.

"We share a common destiny in challenging times of globalization. And in challenging times of globalization, we as Europeans, we are all in the same boat."

The leader of the Alliance of Liberals and Democrats for Europe in the European Parliament said Cameron's speech was "filled with inconsistencies" and showed "a degree of ignorance about how the EU works."

"By holding out the prospect of renegotiating the terms of Britain's membership of the EU and subjecting it to a referendum, David Cameron is playing with fire.

"He can control neither the timing nor the outcome of the negotiations and in so doing is raising false expectations that can never be met."

Philip Gordon, the U.S. assistant secretary for European affairs, also made it clear that there would be consequences for Britain if it either left the EU or played a lesser role in Brussels.

"We have a growing relationship with the EU as an institution, which has an increasing voice in the world, and we want to see a strong British voice in that EU," he told reporters at the U.S. Embassy in London.

"That is in America's interests. We welcome an outward-looking EU with Britain in it."

The New York Times reported Wednesday that the implications of Cameron's speech had "alarmed" the Obama administration and were likely to set up "a divisive debate within Britain and across Europe."